A vehicle air conditioner, which is configured to heat air cooled by an evaporator with use of a heater core to regulate temperature of conditioned air, has conventionally been known to execute an economical control in which refrigerant cooling temperature of the evaporator is increased to save power required by a compressor (see Patent Literature 1, for example).
The vehicle air conditioner includes a refrigeration cycle unit having a compressor driven by a vehicle travel engine. The refrigeration cycle unit thus stops upon start-stop stopping the engine while the vehicle temporarily stops. As already known, the refrigeration cycle unit includes an evaporator provided with a cold energy storage material storing cold energy for limited air cooling upon such start-stop (see Patent Literature 2, for example). Such an evaporator having a cold energy storage function is configured to cool blown air with the cold energy stored in the cold energy storage material while the engine stops and can thus have longer engine stop time.
When the evaporator having the cold energy storage function disclosed in Patent Literature 2 is adopted, decrease in refrigerant cooling temperature of the evaporator leads to shorter freezing time of the cold energy storage material and quick cold energy storage as a basic property required for the evaporator having the cold energy storage function. The refrigerant cooling temperature required for the economy control according to Patent Literature 1 and the refrigerant cooling temperature required by the evaporator having the cold energy storage function according to Patent Literature 2 are thus conflicting and may not be achieved simultaneously.